High-performance liquid chromatographic analysis of α-keto acids produced from amino acid metabolism in oral Bacteroides

Profiles of metabolic α-keto acids were determined by a high-performance liquid chromatographic method and applied to characterization of oral black-pigmented Bacteroides . Each bacterial strain was incubated with amino acids in a chemically defined medium. After production α-keto acids were purified by hydrazide gel column treatment and converted to u.v.-absorbing derivatives. They were analysed by reversed-phase ion-pair chromatography. Black-pigmented Bacteroides species were differentiated into two groups according to production of aromatic α-keto acids. Bacteroides gingivalis, B. endodontalis and B. loescheii produced both ρ-hydroxyphenylpyruvic and phenylpyruvic acids. However, no such α-keto acids were produced by B. levii, B. intermedius and B. denticola . In addition, production profiles of several aliphatic α-keto acids (α-ketoglutaric, pyruvic, α-ketobutyric, α-ketoisovaleric, α-ketoisocaproic, and α-keto-β-methylvaleric acids) separated each individual species in such groups. The present study offers useful chemotaxonomic information on amino acid metabolic activity of oral black-pigmented Bacteroides species.